Vray Glass Alpha

[tom_hh]

Hey Guys, I´m new to vray but not in business. I try to handle the alpha with Vray but it seams it´s a bit different.
I have a scene with two windows in a house. A big towards to the Camera, a smaller backwards from the house. When I set the glas to effect color and alpha, or "all channels", the whole big windiow is cutted out, and I loose the interior of the house. I just want to effect the alpha on that part, where both windows are across and the backgound sphere is visible through the glass.

In other renderer, it´s out of the box, that the alpha is moreless correct displayed.

the same issue happened , when I render a car. usually I just see the background behind the second back window. when I render the scene like I read in the description, the front-window is the alpha, and that is not correct.

any idea? is the only way a workarround with render layers?

thanky for info!

tom

[BeneZ]

The only thing I remember: It must be "color+alpha" or "Color" and set "Max depth" high enough...
Try togggling "exit color" and "caustics", too, there are several combinations
(I haven't tested myself, somebody else will know it better)

[sdelalla]

There are many times you will need your channels to travel through the refractive surfaces (rgb mattes for example). I like to create an extra texture element and put a white ramp into it. It creates a solid white alpha-like channel. If your refraction is on the edge of your scene this could result in values over 1 in your alpha and you may need to create a render layer in that case.

Having a utility render layer with reflection/refraction turned off in the overrides is pretty helpful for all your elements like normals and depth, and then you will get your solid alpha for free as well. Those utility passes don't usually play nice with the 'all channels' check box.